When Slim says that it seems kind of funny that George and Lennie travel together, what is George's response?

At first George is a little bit insulted by this question but the question also povokes George to explain how he ended up with Lennie.  George tells Slim how he had known Lennie’s Aunt Clara who had raised Lennie from a baby. Before Aunt Clara died, George had promised her to become Lennie's caregiver.